Electron discharge device



May 19, 1936. KNIEPKAMP 2,041,292

ELECTRON DI SCHARGE DEVICE Filed Feb. 9, 1955 INVENTOR.

HEINRICH KNIEPKAMP ATTORNEY.

Patented May 19, 1936 UNITED STATES PATENT OFFICE ELECTRON DISCHARGE DEVICE poration of Germany Application February 9, 1935, Serial No. 5,702 In Germany July 24, 1933 6 Claims.

My invention relates to electron discharge devices having a gaseous atmosphere, and more particularly to an improved form of lead-in and electrode support for such electron discharge "devices.

In electron discharge devices, particularly those having a gaseous atmosphere for example, rectiflers, it is quite general practice to use graphite electrodes for the anodes or plates. These elec- 10 trodes are secured upon electrode supporting wires which are sealed in by one of several wellknown methods. Especially in the case of anodes mounted in rectifiers, power tubes and the like, very marked heating of the anode occurs during operation. As a result of this heating, gases occluded in the anode are liberated, and this leads to erratic operation. In order that the escape of gas during operation may be avoided, it is general practice to degas electrodes of an electron discharge device during the manufacture, and this degassing is usually done by means of high frequency currents. For this purpose the graphite anode or plate may be provided with an iron core in which eddy-currents are set up, which in turn results in the heating. Anodes of this kind are comparatively complicated, and there is the danger that the graphite parts may become loose on their supports during operation, thereby causing trouble.

8 In the kind of electrodes considered cooling of the electrodes by means of thermal conduction is not readily accomplished. The use of separate cooling means involves complications in construction, and is worth while only for large units.

Another disadvantage of the conventional cooling construction is that the electrode support wires must be surrounded by an insulation tube or the like in order to preclude all chances of a discharge being started at the support wires. From experience it has been found that the provision of such an insulation tube does not provide an absolute safeguard against the discharge starting at undesired points because the insulation tube may become defective and there may he places where the supporting wire is not completely surrounded by the tube.

It has been proposed to provide the lead-in in the form of an annular metal cap or cuff sealed to the glass envelope in such a way that the in- I terior of the cap or cuff communicates with the interior of the envelope. In discharge devices of this kind the electrodes, especially graphite electrodes, are so arranged that they fit closely into the concave end of the cap and extend into the envelope of the tube. The electrodes have also been surrounded with a metallic sheath which is fitted so closely or with so little clearance between the electrode and inner wall of the sheath that with a given gas pressure the dis charge is unable to pass thru the gap between the sheath and electrode and start from the end of the electrode within the sheath. However, in the forms of construction described it is difficult to insure sufiicient cooling of the metallic sheath of the electrode, and this is of great importance in the case' of high power discharge tubes.

It is therefore an object of my invention to provide an improved type of lead-in and electrode support for electron discharge devices, and which provides for proper cooling of the electrode and support.

In accordance with my invention, in electron discharge tubes which are provided with a current lead-in thru an annular sealed-in metallic cap or cuff, the convex end of which is turned outwardly, the electrode, particularly if a graphite electrode, fits directly into the metallic cap and extends into the envelope of the tube. This cap is sealed to one end of .an insulating sleeve, the other end of which is sealed to a cylindrical metallic tube provided with an enlarged end which is in turn sealed to the envelope of the tube. This cylindrical metallic tube is provided with a metallic sheath or shield supported by the metallic tube and surrounding and spaced from the electrode extending within the envelope. The metallic cap and cylindrical tube are provided with cooling fins.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure l is a vertical section of a lead-in and electrode support embodying my invention; Figure 2 is a perspective view with parts broken away of details of a modification of the lead-in and support shown in Figure 1.

According to my invention there is sealed to the discharge vessel I preferably of the gaseous discharge type at the point marked 2 a metallic tube 3, which at its lower end 4 is enlarged or flared outwardly. This tube 3 is provided with a sheath or shield 5 which extends downwardly around but out of contact with the anode 5, which is preferably made of graphite. The upper end of the metallic tube 3 is sealed to a tubular member or sleeve 1 of insulation material, for example glass. Sealed to the upper or outer end of the sleeve 01' collar 1 is themetal cup-shaped cap 8 which seals the envelope and supports the elec-.

trode 8. Both the tube 3 as well as the metal cap 8 may be furnished with cooling means 9 and iii. For example, cooling fins or vanes may be fitted on, or else a cooling jacket may be provided for circulating the cooling fluid.

The diameter of the electrode. 6 fitted into the cap 8 should be such that suflicient heat conductivity will be assured under working conditions when heated to about 400 C. so that the temperature of the electrode will remain low enough to prevent out-gassing oi. the electrode. The cap I itself is preferably made from thin copper sheet, the thickness of the latter being such that, upon evacuation, the outer air pressure will press the copper firmly against the electrode 6 thereby providing a firm support. In some instances it may be desirable to provide the electrode itself with slots or recesses l l as shown in Figure 2, into which the metallic cap is forced by action of the air pressure or the aid of a tool.

While I have indicated the preferred embodiments of my invention oi which I am now aware and have also indicated only one specific applica-- tion for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims.

What I claim as new is:--

1. A lead-in and support for an electron discharge device having an evacuated envelope and comprising a metallic cup-shaped cap, a tubular member of insulating material sealed at one end to the open end of said metallic cap, a metallic tube sealed to the other end of said tubular member and having a flared end sealed to the envelope of the electron discharge device, an electrode positioned within and supported by said cap and extending thru said tubular member and thru but out of contact with said metallic tube into the envelope, and a metallic sheath secured to said metallic tube and closely surrounding but out of contact with the end of said electrode extending into the envelope.

2. A lead-in and support for an electron discharge device having an evacuated envelope and comprising a metallic cup-shaped cap, a tubular member of insulating material sealed at one end to the open end oi said metallic cap, a metallic tube sealed to the other end oi! said tubular member and having a flared end sealed to the envelope of the electron discharge device, an electrode positioned within and supported by said cap and extending thru said tubular member and metallic tube into the envelope, said metallic tube closely surrounding a portion or the extending end of said electrode but out of contact therewith and a metallic sheath secured to said metallic tube and closely surrounding but out of contact with the extending end of said electrode, the spacing between the metallic tube and sheath and the elec trode being so small that with a predetermined gas pressure the discharge cannot pass thru the spacing between the electrode and tube or shield.

3. A lead-in and support for an electron discharge device having an evacuated envelope and comprising a metallic cup-shaped cap, a tubular member of insulating material sealed at one end to the open end of said metallic cap, a metallic tube sealed to the other end of said tubular member and having a flared end sealed to the envelope of the electron discharge device, an electrode positioned within and supported by said cap and extending thru said tubular member and metallic tube into the envelope, said metallic tube closely surrounding a portion of the extending end or said electrode'but out or contact therewith and a metallic sheath secured to said metallic tube and closely surrounding but out of contact with the extending end of said electrode, and cooling fins on said metallic cap and sleeve.

4. A lead-in and support for an electron discharge device having' an evacuated envelope and comprising a metallic cup-shaped cap, a tubular member of insulating material sealed at one end to the open end of said metallic cap, a metallic tube sealed to the other end of said tubular member and having a flared end sealed to the envelope of the electron discharge device, a carbon electrode positioned within and supported by said cap and extending thru said tubular member and metallic tube into the envelope, said metallic tube closely surrounding a portion of the extending end oi said electrode but out of contact therewith and a metallic sheath secured to said metallic tube and closely surrounding but out of contact with the extending end of said electrode, said electrode being of graphite, and so dimensioned that the heat conductivity to said cap under working conditions will maintain the temperature of the electrode below the outgassing temperature.

5. A lead-in and support for an electron discharge device having an evacuated envelope and comprising a metallic cup-shaped cap, a tubular member 'of insulating material sealed at one end to the open end of said metallic cap, a metallic tube sealed to the other end of said tubular member and having a flared end sealed to the envelope of the electron discharge device, an electrode positioned within and supported by said cap and extending thru said tubular member and metallic tube into the envelope, said metallic cap being of comparatively thin sheet metal whereby upon evacuation of the discharge tube the cap will be firmly pressed against the electrode by atmospheric pressure, said metallic tube closely surrounding a portion of the extending end oi. said electrode but out of contact therewith and a metallic sheath secured to said metallic tube and closely surrounding but out of contact with the extending end of said electrode.

6.. A lead-in and support for an electron discharge device having an evacuated envelope and comprising a metallic cup-shaped cap, a tubular member of insulating material sealed at one end to the open end of said metallic cap, a metallic tube sealed to the other end of said tubular member and having a flared end sealed to the envelope of the electron discharge device, an electrode positioned within and supported by said cap and extending thru said tubular member and metallic tube into the envelope, said metallic tube closely surrounding a portion of said electrode but out of contact therewith and a metallic sheath secured to said metallic tube and closely surrounding but out of contact with the extending end of said electrode, said metallic cap being of thin sheet metal, said electrode being provided with recesses into which the metal cap is forced by atmospheric pressure. 

